Valve porting arrangement for a gerotor

ABSTRACT

A fluid displacing device having a fixed internal gear in mesh with a planetating external gear to expand and contract pressure chamber formed between the teeth of the internal gear causing flow of fluid to and from the pressure chambers alternately placed in fluid communication with inflow and outflow ports by a flow distributing arrangement which includes an externally grooved, rotary slide coaxially coupled to the power shaft and mounted on the coupling shaft to which the external gear is pinned. Continuous fluid communication is maintained by the external grooves at the end of the rotary slide in sliding contact with the external gear.

United States Patent Liebert June 3, 1975 [54] VALVE PORTING ARRANGEMENTFOR A 3,283.723 11/1966 Charlson 418/61 13 3,289,542 12/1966 Fikse 1 1.7 418/61 B GEROTOR 3,289,601 12/1966 Compton .6 418/61 B Inventor:Karl-Heinz Liebert. Schwabisch 3,385,057 5/1968 P1111161 et a1... 418/61B Gmund, Germany 3,446,153 5/1969 Easton 418/61 8 [73] Assignee:Zahnradtabrik Friedrichshafen AG,

Germany Primary Examiner-John J. Vrabhk Attorney, Agent, orFirm-Zalkind, Hornet & Shuster [22] Filed: Apr. 30, 1973 A fluiddisplacing device having a fixed internal gear [30] Forelgn ApphcauonPflomy Dam in mesh with a planetating external gear to expand and P 11972 Germany 2221183 contract pressure chamber formed between the teethof the internal gear causing flow of fluid to and from Cl 418/61l37/625-24 the pressure chambers alternately placed in fluid com- [5l]lnt- C Flllc U F03C munication with inflow and outflow ports by a flow[53] Field 01 Search 418/61 B; di tributing arrangement which includesan externally 13 /6 5-2 grooved, rotary slide coaxially coupled to thepower shaft and mounted on the coupling shaft to which the 156] e fiCited external gear is pinned. Continuous fluid communica- UNITED STATESPATENTS tion is maintained by the external grooves at the end 2,121 4556/1938 Ten Broek 64 7 of the rotary shde sliding with the external2,153,093 4/1939 Magee et a1. 64/7 g 3,270,683 9/1966 McDermott 1 1 1418/61 B 3,277,833 10/1966 Hudgens 418/61 B 16 Clam, 8 D'hwmg F'ghres 2817 11 III 1V V 24 13 VI h 11 12 A I r-/ I 8 5 /i\\ I'n iv v IV 2 l 6 IL15 3 PATENTEUJM 3 1975 SHEET FIG.1

PATENTEDJUH 3 ms SHEET FIGZ PATENTEDJUH .975 v .887.308

FIG. 6

VALVE PORTING ARRANGEMENT FOR A GEROTOR This invention relates to ahydrostatic pump or fluid motor, particularly useful in hydrostaticpower steering systems for motor vehicles.

Fluid displacing devices having a fixed toothed ring with an internaltooth profile and an external gear having one tooth less than said ringso as to produce a planetary movement of an external gear, are wellknown. A fluid distributing arrangement is generally rotatable with theexternal gear about its axis and includes a control valve havingchannels leading to each fluid pressure chamber formed between the teethof the tooth ring. Control openings corresponding in number to twice thenumber of teeth of the toothed ring are disposed in the housing forcooperation with said channels. The fluid distributing arrangementalternately establishes fluid communication between the pressurechambers and separate fluid conduits conducting fluid medium to and fromthe fluid displacement device.

Such rotary fluid displacing devices with a rotating distributor controlvalve deliver a relatively large mass of fluid per rotation of thedriving shaft at a low speed, in the case ofa pump operation, or in thecase of motor operation, a relatively large driven torque and fluidabsorption volume for a low driven speed. Such devices are thereforeused in hydrostatic steering systems for motor vehicles as a hydraulicauxiliary power assist under control of the steering wheel or as ahydraulic auxiliary power source operable by the steering wheel.

In one known type of rotary fluid displacing device fluid pressurechannels are formed in the gear and lead to gaps between the teeth andto openings in fixed walls of the housing forming part of a fluiddistribution system, so that movement of the gear around its center byone tooth pitch, completes a control cycle of the distribution system.

In another type of fluid displacing device, a cylindrical rotating slidevalve rotating with the driving or driven shaft in coaxial relationthereto, has longitudinal grooves on its outside cylindrical surface,which are alternately connected with separate pressure lines, and tochannels leading to the pressure chambers formed between the teeth ofthe internally toothed ring.

In yet another known type of fluid displacing device operating as arotating piston engine, a rotary piston is mounted in a housing, thecross section of which constitutes a triangle with rounded corners andconnected by means of a drive shaft with the driving or driven shaft, sothat the rotary piston upon one turn of the shaft by 360 rotates anumber of times about its center, corresponding to the number of teethof the rotary piston, as it travels along a circular path around theaxis of the housing, in a direction opposite to the rotational directionof the shaft. In such case, discharge of the operating medium iscontrolled by cooperation between control channels in one surface of therotary piston and a number of control openings arranged in a wall of thehousing adjacent to said channels, as a result of which said openingsalternately communicate with the control channels of the rotary piston.

In still another known rotary piston engine, the gear is connected withthe main shaft by means of a drive shaft, so that the cylindrical,rotary slide of the distributor at the rotational speed of the mainshaft and coaxial therewith, rotates synchronously with the rotationalmovement of the piston about its own axis. The rotary slide at the sametime has a number of longitudinal grooves corresponding to double thenumber of teeth of the gear, which are connected in an alternatingsequence each time with a separate pressure line and cooperate withchannels disposed in the housing leading to the root of the teeth of thetoothed ring.

In the foregoing rotary piston engines, the flow of pressure liquid isthrottled abruptly because of the arrangement of channels leading fromthe displacement chamber to the connecting lines and by the directionalflow changes and cross sectional passage constrictions. As a result ofthese flow losses, the mass of fluid displaced in the case of a liquidpump, is reduced by the cavitation occurring in the suction lines, whilein the case of a liquid motor, drive torque is decreased by reason ofpressure losses.

Therefore an important object of the present invention is to provide arotary piston engine with rotating distributor control, wherein anoptimum degree of filling is effected with small losses of pressure inthe supply channels conducting flow to the pressure medium operatingchambers formed between the toothed profiles of the external gear andthe internally toothed ring.

In order to achieve the foregoing objective, the invention includes arotary slide, rotatable with the external gear which in turn is coupledin a manner known to the driving shaft by means of coupling shaft. Therotary slide is connected slidingly at one axial end with a surface ofthe gear and has longitudinal grooves extending axially on its radiallyouter or outside cylindrical sur face communicating on said one axialend with the gaps between the teeth of the gear. The grooves are alsoaxially aligned with control openings in the housing to providealternating fluid communication with separate pressure lines along thecylindrical surface.

Also, the longitudinal grooves disposed on the outside surface of therotary slide, have enlargements at the ends in a sliding contact withone axial surface of the gear to advantageously conduct flow between theoperating chambers and the inflow and outflow ports with a minimalamount of throttling.

The invention will be explained in more detail hereafter with additionalfeatures shown constituting part of one embodiment shown by way ofexample in the drawings, in which:

FIG. 1 shows a longitudinal section view through a rotary piston engineconstructed in accordance to the present invention.

FIGS. 26 are transverse section views taken through planes indicated bysection lines lI-II, lII--III, IVIV, V-V and VI-VI of FIG. 1.

FIG. 8 shows a modified form of the rotary piston engine constructed inaccordance to the present invention.

FIG. 7 is a side elevation view of the rotary slide.

An internal toothed ring or gear 1 as shown in FIG. 1, is disposedbetween an end cover 2 and a housing body 3 to which it is fixed bymeans of screws 4. An externally toothed gear 5 having one tooth lessthan the toothed ring 1, forms with said toothed ring 1 operatingchambers 6 radially between the teeth of the two gears and axiallybetween the confronting surfaces of the cover wall 2 and the housing 3.

The gear 5 is connected for rotation with a driving shaft 8 by means ofa coupling shaft 7. Two driver pins 9 and and the coupling shaft 7 fonna universal, articulated connection between the gear 5 and the drivingshaft 8. The coupling shaft 7 is fixed in an axial direction in thedriving shaft 8 by a front surface 11 and in the gear 5 by a buffer disk12 abutting the cover wall 2.

A flow controlling member in the form of a rotary slide 13 is coaxiallymounted relative to the driving shaft 8 in the housing 3 and coupled tothe driving shaft 8 by means of a coupling pin 14 for rotationtherewith. In order to avoid misalignment between the driving shaft 8and the rotary slide 13, limited radial displacement relative to eachother is accomodated by the coupling. Alternatively, the rotary slide 13could be made an integral component of the driving shaft 8 as shown inFIG. 8 to avoid misalignment.

A needle thrust bearing 15, axially positions the driving shaft 8relative to an adjusting disk 16, the thickness of which is selected toobtain the required axial clearances for sliding contact between therotary slide 13 at one axial end and the gear 5 as shown in FIG. 1.

The gear 5 is coupled to the driving shaft 8 as aforementioned so thatupon each revolution of the driving shaft 8, the gear 5 will rotateabout its own axis in a reverse direction a number of revolutionscorresponding to the relative numbers of teeth of the gear 5 and ring 1,as the gear 5 is carried in a circular path about the axis of the fixedtoothed ring 1.

Longitudinal grooves 17, leading to the gaps between the teeth of thegear 5, are formed on the outside cylindrical valve surface of therotary slide 13. The longitudinal grooves 17 have enlargements 18 on thefront axial end surface of the rotary slide 13 adjacent to the gear 5,to enlarge the transitional flow area to the operating chambers 6. Sinceboth the rotary slide 13 as well as the gear 5 are rotatably coupled tothe driving shaft 8, and the gear 5 planetates in a direction oppositeto the rotary movement of the driving shaft, during expansion andcontraction of the volume of the operating chamber 6 there is relativedisplacement between the rotary slide 13 and the gear 5 in synchronismwith the rotational movements. In this manner, as expansion of eachoperating chamber 6 occurs, there is a corresponding enlargement of thetransitional flow area to an associated longitudinal groove 17 in therotary slide 13 and thus a continuous filling and emptying of theoperating chambers 6. In order to avoid abrupt change in flow of fluidpressure medium, a continuous transition passage from the longitudinalgrooves 17 to the volumetrically variable pressure spaces or operatingchambers 6, is provided.

The longitudinal grooves 17 are axially aligned with control openings 21or 22 formed in the housing 3 as shown in FIGS. 4 and 5 so that thegrooves 17 communicate alternately with separate ports 19 or 20 for theinflow or the return flow of a fluid pressure medium. The number ofcontrol openings 21 and 22 correspond to double the number of teeth ofthe toothed ring 1. The control openings 21 or 22 which arecircumferentially spaced from each other by one tooth pitch of theinternal teeth of ring one, are displaced from the internal teeth oneither side by one-fourth of the tooth pitch of the internally toothedring 1 shown in the drawings.

The control openings 21 are connected with an annular channel 23disposed in the housing 3 and the control openings 22 with acorresponding annular channel 24. The annular channel 23 is connected byan axial passage to the port 19 while the annular channel 24 isconnected by passage 26 to the port 20.

The longitudinal grooves 17 in the rotary slide 13 act, together withthe control openings 21 and 22 in the housing 3, in such a way, that theoperating chambers 6 lying on one side of a line passing through thecenters of the gear 5 and toothed ring 1 as viewed in FIG. 2, areconnected by the control openings 21 with one port 19 while theoperating chambers 6 lying on the other side of the separating line areconnected to the other port 20 by the other control openings 22.

The control openings 21 as viewed in FIG. 4 are circumferentially spacedfrom the control openings 22 by one half of the tooth pitch of the teethof the toothed ring 1. In order to obtain large transitional flow areasduring transitional flow from the longitudinal grooves 17 to the annularchannels 23 and 24, the control openings 21 and 22 are developed aslongitudinal slits running axially in the housing 3.

One of the ports 20 is effectively connected with an annular channel 27disposed in the housing 3 as seen in FIG. 6, in order that all spaces inthe bores formed in the gear 5, the rotary slide 13, the driving shaft 8as well as the housing 3, can be vented through one of the pressurefluid lines and filled with a fluid pressure medium.

To radially fix the driven pin 10, it is necked down to flats 10aparallel to one another in its central part, which are engaged by thefork-shaped end of the coupling shaft 7.

A cylindrical casing or shell 28 enclosing the housing 3, the toothedring 1 and the coverwall 2, seals the annular channels 23 and 24 fromeach another and also seals the toothed ring 1 against leakage past thecover wall 2.

It will be apparent that flow to and from the operating chambers 6 isconducted through the longitudinal grooves 17 in the rotary slide 13which communicate with the operating chambers. The transitional flowpassages 18 between the longitudinal grooves and the operating chambers,having enlarged flow areas, reduce the flow velocity of the fluidpressure medium to and from the operating chambers. The inflow anddischarge of the fluid medium to and from the operating chambers occurswith only one directional change in the fluid stream within the controlchannels. Also, the transitional flow passage at 18 between eachoperating chamber and a longitudinal groove of the rotary slide,increases in flow area in synchronism with expansion of the associatedoperating chamber. The rotary fluid displacing device described, thusoperates as a pump or motor with reduced fluid flow losses.

I claim:

1. In a fluid displacing device, a housing (3) having separate ports (24and 25) and to which an internal gear (1) is fixed, an external gear (5)in mesh with the internal gear to form pressure chambers (6) within theinternal gear, a power shaft (8) and articulated means (7) coupling theshaft to the external gear for imparting planetary movement theretocausing expansion and contraction of said pressure chambers, a fluiddistributing system including a flow controlling member (13) mounted onthe coupling means having a radially outer valve surface and an axialend surface in sliding contact with the external gear, means directlyconnecting the flow controlling member to the power shaft for rotationthereof at the same speed as the external gear to control flow of fluidat said valve surface to and from the ports and conduit means (17-18)mounted in the flow controlling member to form passages in continuousfluid communication with the pressure chambers and said valve surface ofthe flow controlling member for conducting said flow of fluid betweensaid ports and said pressure chambers during rotation of the powershaft.

2. The combination of claim 1 including axial thrust bearing meansaxially positioning the flow controlling member within the housing forestablishing a predetermined clearance between the external gear and theflow controlling member.

3. The combination of claim 1 wherein said coupling means includes acoupling shaft having opposite ends, one of which is provided with afork formation, a driver pin having and bearing portions pivotallyconnected to the power shaft and an intermediate portion of reducedcross-section presenting parallel flats engaged by the fork formation atsaid one of the ends of the coupling shaft and means pivotallyconnecting the other of the ends of the coupling shaft to the externalgear.

4. The combination of claim 1 including a common sealing shell enclosingboth the housing and the internal gear for confining flow between thepressure chambers and the separate passages in the housing.

5. The combination of claim 1 wherein the flow controlling member ismade an integral component of the power shaft.

6. The combination of claim 1 wherein said conduit means comprises aplurality of external grooves opening radially outwardly and extendingaxially from one axial end of the flow controlling member, said groovesbeing circumferentially spaced from each other by one tooth pitch of theexternal gear, each of said grooves having a flow transition enlargementat said one axial end in fluid communication with the pressure chambers.

7. The combination of claim 1 wherein said conduit means comprisesseparate, axially extending grooves (17) formed externally on said flowcontrolling member and opening radially outwardly, said grooves beingcross-sectionally enlarged (18) adjacent one axial end of the flowcontrolling member and opening in an axial direction to establish saidcontinuous fluid communication with the pressure chambers.

8. The combination of claim 7 wherein said housing includes axiallyextending openings (21 and 22) aligned with the grooves to establishseparate passages from the ports.

9. The combination of claim 8 wherein said control openings arecircumferentially spaced from the teeth of the internal gear by onequarter of the circular tooth pitch associated with the internal gear.

10. The combination of claim 9 wherein the control openings in one ofthe separate passages are circumferentially spaced from the controlopenings in the other of the separate passages by one half the circulartooth pitch of the internal gear.

11. The combination of claim 8 including axial thrust bearing meansaxially positioning the flow controlling member within the housing forestablishing a predetermined clearance between the external gear and theflow controlling member.

12. The combination of claim 11 wherein said control openings arecircumferentially spaced from the teeth of the internal gear byone-quarter of the circular tooth pitch associated with the internalgear.

13. The combination of claim 12 wherein the control openings in one ofthe separate passages are circumferentially spaced from the controlopenings in the other of the separate passages by one half the circulartooth pitch of the internal gear.

14. The combination of claim 13 wherein said coupling means includes acoupling shaft having opposite ends, one of which is provided with afork formation, a driver pin pivotally connected to the power shafthaving end bearing portions and an intermediate portion of reducedcross-section presenting parallel flats engaged by the fork formation atsaid one of the ends of the coupling shaft and means pivotallyconnecting the other of the ends of the coupling shaft to the externalgear.

15. The combination of claim 14 including a common sealing shellenclosing both the housing and the internal gear for confining flowbetween the pressure chambers and the separate passages in the housing.

16. In combination with a fluid displacing device having a housing (3)provided with inlet and outlet ports (19 and 20), an internal gear (1)fixed to the housing, an external gear (5 enmeshed with the internalgear to form volumetrically variable pressure spaces (6) within theinternal gear, a power shaft (8), and articulated coupling means (7)drivingly connecting the power shaft to the external gear; fluiddistributing means for conducting a pressure medium between the ports inthe housing and said pressure spaces, comprising an axially elongatedmember (13) having opposite axial ends and an external cylindrical valvesurface, a plurality of Iongitudinal grooves (17) formed in saidexternal valve surface and extending from one of said axial ends towardlocations spaced from the other of the axial ends, means coupling themember at said other of the axial ends to the power shaft for rotationat the same speed as the external gear to control fluid communicationbetween the ports and the grooves at said external valve surface of themember, said one of the axial ends of the member being in slidingcontact with the external gear and provided with enlargements of thegrooves to form continuous transitional passages between the grooves andthe pressure spaces.

I! i l l

1. In a fluid displacing device, a housing (3) having separate ports (24and 25) and to which an internal gear (1) is fixed, an external gear (5)in mesh with the internal gear to form pressure chambers (6) within theinternal gear, a power shaft (8) and articulated means (7) coupling theshaft to the external gear for imparting planetary movement theretocausing expansion and contraction of said pressure chambers, a fluiddistributing system including a flow controlling member (13) mounted onthe coupling means having a radially outer valve surface and an axialend surface in sliding contact with the external gear, means directlyconnecting the flow controlling member to the power shaft for rotationthereof at the same speed as the external gear to control flow of fluidat said valve surface to and from the ports and conduit means (17-18)mounted in the flow controlling member to form passages in continuousfluid communication with the pressure chambers and said valve surface ofthe flow controlling member for conducting said flow of fluid betweensaid ports and said pressure chambers during rotation of the powershaft.
 1. In a fluid displacing device, a housing (3) having separateports (24 and 25) and to which an internal gear (1) is fixed, anexternal gear (5) in mesh with the internal gear to form pressurechambers (6) within the internal gear, a power shaft (8) and articulatedmeans (7) coupling the shaft to the external gear for impartingplanetary movement thereto causing expansion and contraction of saidpressure chambers, a fluid distributing system including a flowcontrolling member (13) mounted on the coupling means having a radiallyouter valve surface and an axial end surface in sliding contact with theexternal gear, means directly connecting the flow controlling member tothe power shaft for rotation thereof at the same speed as the externalgear to control flow of fluid at said valve surface to and from theports and conduit means (17-18) mounted in the flow controlling memberto form passages in continuous fluid communication with the pressurechambers and said valve surface of the flow controlling member forconducting said flow of fluid between said ports and said pressurechambers during rotation of the power shaft.
 2. The combination of claim1 including axial thrust bearing means axially positioning the flowcontrolling member within the housing for establishing a predeterminedclearance between the external gear and the flow controlling member. 3.The combination of claim 1 wherein said coupling means includes acoupling shaft having opposite ends, one of which is provided with afork formation, a driver pin having end bearIng portions pivotallyconnected to the power shaft and an intermediate portion of reducedcross-section presenting parallel flats engaged by the fork formation atsaid one of the ends of the coupling shaft and means pivotallyconnecting the other of the ends of the coupling shaft to the externalgear.
 4. The combination of claim 1 including a common sealing shellenclosing both the housing and the internal gear for confining flowbetween the pressure chambers and the separate passages in the housing.5. The combination of claim 1 wherein the flow controlling member ismade an integral component of the power shaft.
 6. The combination ofclaim 1 wherein said conduit means comprises a plurality of externalgrooves opening radially outwardly and extending axially from one axialend of the flow controlling member, said grooves being circumferentiallyspaced from each other by one tooth pitch of the external gear, each ofsaid grooves having a flow transition enlargement at said one axial endin fluid communication with the pressure chambers.
 7. The combination ofclaim 1 wherein said conduit means comprises separate, axially extendinggrooves (17) formed externally on said flow controlling member andopening radially outwardly, said grooves being cross-sectionallyenlarged (18) adjacent one axial end of the flow controlling member andopening in an axial direction to establish said continuous fluidcommunication with the pressure chambers.
 8. The combination of claim 7wherein said housing includes axially extending openings (21 and 22)aligned with the grooves to establish separate passages from the ports.9. The combination of claim 8 wherein said control openings arecircumferentially spaced from the teeth of the internal gear by onequarter of the circular tooth pitch associated with the internal gear.10. The combination of claim 9 wherein the control openings in one ofthe separate passages are circumferentially spaced from the controlopenings in the other of the separate passages by one half the circulartooth pitch of the internal gear.
 11. The combination of claim 8including axial thrust bearing means axially positioning the flowcontrolling member within the housing for establishing a predeterminedclearance between the external gear and the flow controlling member. 12.The combination of claim 11 wherein said control openings arecircumferentially spaced from the teeth of the internal gear byone-quarter of the circular tooth pitch associated with the internalgear.
 13. The combination of claim 12 wherein the control openings inone of the separate passages are circumferentially spaced from thecontrol openings in the other of the separate passages by one half thecircular tooth pitch of the internal gear.
 14. The combination of claim13 wherein said coupling means includes a coupling shaft having oppositeends, one of which is provided with a fork formation, a driver pinpivotally connected to the power shaft having end bearing portions andan intermediate portion of reduced cross-section presenting parallelflats engaged by the fork formation at said one of the ends of thecoupling shaft and means pivotally connecting the other of the ends ofthe coupling shaft to the external gear.
 15. The combination of claim 14including a common sealing shell enclosing both the housing and theinternal gear for confining flow between the pressure chambers and theseparate passages in the housing.